CODEWITHSUNDEEP
r
Rene B.
Rene B.

Reputation: 7424

How to convert a date column of a R dataframe to a certain string format

I want to convert a column of a dataframe in R into a new column with a string format and extract for example only the day or the month. The format of the dataframe could look like this, where the date has already the type Date:

Name,Date,Salary
Bob,12/31/18,1000
Alice,10/28/18,100
John,05/06/17,200

So the target df should look like this:

Name,Date,Day,Month,Salary
Bob,12/31/18,31,12,1000
Alice,10/28/18,28,10,100
John,05/06/17,06,05,200

Upvotes: 1

Views: 576

Answers (2)

G. Grothendieck
G. Grothendieck

Reputation: 270428

Use format. The [...] part at the end can be omitted if the order of columns is not important.

transform(DF, Day = format(Date, "%d"), Month = format(Date, "%m"))[
  c("Name", "Date", "Day", "Month", "Salary")]

giving:

   Name       Date Day Month Salary
1   Bob 2018-12-31  31    12   1000
2 Alice 2018-10-28  28    10    100
3  John 2017-05-06  06    05    200

There is also some question of whether you really need to add Day and Month columns in the first place given that the Date is already a column. It might be more convenient to extract it on the fly when you need it depending on what you are doing with it.

Note

The input in reproducible form is assumed to be:

Lines <- "Name,Date,Salary
Bob,12/31/18,1000
Alice,10/28/18,100
John,05/06/17,200"

DF <- read.csv(text = Lines)
DF$Date <- as.Date(DF$Date, "%m/%d/%y")

Upvotes: 2

Tim Biegeleisen
Tim Biegeleisen

Reputation: 522797

For a base R solution, we can try using first as.Date to convert your string dates to bona fide R dates. Then, we can convert those dates to POSIXlt objects, in order to extract the day and month components.

x <- "12/31/18"
date <- as.Date(x, "%m/%d/%y")
day <- as.POSIXlt(date)$yday + 1
month <- as.POSIXlt(date)$mon + 1

day
month

[1] 365
[1] 12

Demo

Upvotes: 2

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